7.1.1 USB Type C Basic

For a detailed description of the Type-C spec refer to the USB-IF website to download the latest released version. Some of the basic concepts of the Type-C spec that pertains to understanding the operation of the TPS25820/21 (a Downward Facing Port, DFP device) are described as follows.

USB Type-C removes the need for different plug and receptacle types for host and device functionality. The Type-C receptacle replaces both Type-A and Type-B receptacles since the Type-C cable is plug-able in either direction between host and device. A host-to-device logical relationship is maintained via the configuration channel (CC). Optionally hosts and devices can be either providers or consumers of power when USB PD communication is used to swap roles.

All USB Type-C ports operate in one of below three data modes:

• Host mode: the port can only be host (also provider of power)
• Device mode: the port can only be device (also consumer of power)
• Dual-Role mode: the port can be either host or device

Port types:

• DFP (Downstream Facing Port): Host, specifically associated with flow of data (Host or Hub) in a USB link
• Source: Port that asserts Rp (pull-up resistor) on CC pin and provides power on VBUS when attached to a Sink (device). At power-up a DFP is a source.
• UFP (Upstream Facing Port): Device, specifically associated with flow of data (device) in a USB link
• Sink: Port that asserts Rd (pull-down) on CC pin and consumes power from VBUS when attached. At power-up a UFP is a sink
• DRP (Dual-Role Port): Host or Device

Valid Source-to-Sink connections:

• Table 1 describes valid Source-to-Sink connections
• Source to Source or Sink to Sink have no function